Out of the Shadow of a Giant: How Newton Stood on the Shoulders of Hooke and Halley. John Gribbin
to measure the height of a star above the horizon, or the angular distance between two astronomical objects. Prior to Hooke’s invention, this involved looking through a telescope or open sight at the horizon, holding the instrument steady (easy for astronomers on solid Earth, less easy for mariners on the deck of a heaving ship), and moving a second telescope (or sight) on an arm hinged to the first one on to the target star (or Sun), then measuring the angle between the two jointed arms. Hooke’s ingenious idea was to attach a small mirror to the moveable arm of the instrument, which reflected an image of the object being observed (the target star, or the Sun) on to a second mirror and along the first (indeed, now the only) sighting arm, while this was pointed at the horizon. The operator could then see both the horizon and an image of the target along the same sight, and the angle of the moveable arm could be adjusted until the image of the target seemed to be sitting on the horizon. The angle when this occurred could be read off from a curved, graduated scale on the instrument.fn3
Hooke’s main interest in developing the instrument was astronomical – he told the Society, in the run-up to the intended lecture, that he had a method to determine accurately the angular distances of stars relative to the Moon, which had a direct bearing on the longitude problem. But had he not been distracted by other work, and been able to develop the idea, it would surely soon have been applied to navigation. Hooke’s instrument was so completely forgotten that in 1691 Edmond Halley reinvented it, but quickly withdrew his claim for priority when it was pointed out that his friend Hooke had come up with the idea twenty-five years earlier. And in 1699, Isaac Newton claimed to have invented such a device, which roused the by then ailing Hooke to drag himself along to the next meeting of the Royal to remind them of his priority. The idea only really took off, however, after 1731, when John Hadley demonstrated his own version of the sextant to the Royal Society.
In September 1666, the City of London was, as far as fire was concerned, an accident waiting to happen. Many of the lanes were only five or six feet wide, and the upper storeys of the buildings hung over the lanes so that they almost touched, perhaps with a foot of space through which a strip of sky might be visible. The houses themselves were timber-framed, with a lathe and plaster infill. And everything was tinder dry, following a long, hot summer. In addition, on 2 September, when fire broke out in a bakehouse in Pudding Lane, there was a strong north-easterly wind, which fanned the flames and swept them westward and down to the Thames. The conflagration raged for three days before a slackening wind enabled the firefighters to get on top of it, and by Thursday most of the City was a smouldering ruin. The Royal Exchange, source of Sir Thomas Gresham’s wealth, was gone, but the fire had stopped about 200 yards from Gresham College, in the north-eastern (upwind) quarter of the City. Only about 75 acres out of just over 400 acres within the City walls survived, while a further 63 acres to the west, covering Holborn and Fleet Street, had also gone. The old St Paul’s Cathedral was lost, together with 90 churches, 52 Livery Company halls and more than 13,000 houses.fn4 An estimated 100,000 people lived in the City at the time, and three-quarters of these were now forced to camp outside in the open spaces beyond the walls, but fortunately there was only relatively minor loss of life, perhaps a few hundred people.
The City was governed by a Court of Aldermen, or corporation, under the Lord Mayor; having lost their Guildhall home, the Court moved into Gresham College, meeting there for the first time on Thursday 6 September, and forcing all the professors and their tenants (legal and illegal) out, except for the household of one man – Robert Hooke, who had good City connections and was seen as a valuable person to have on hand for advice and help. The Royal was able to find accommodation in Arundel House on the Strand, and continued to function – which meant that Hooke and his operator had to trek about a mile and a half across the ruins and up Fleet Street with the equipment for the demonstrations he was still required to perform. The astonishing thing is that he did continue to carry out a full programme for the Royal, and give his Gresham and Cutlerian lectures, even though he now undertook a task that to anyone else would have been a full-time occupation: supervising the rebuilding of London.
While the fires were still smouldering, several people presented plans for the rebuilding of the city to the King. The Cityfn5 had moved with impressive speed to restore order, issuing instructions for clearing the rubble, setting up temporary markets, and so on. They recognised the need for swift action on a formal rebuilding programme to prevent unregulated reconstruction higgledy-piggledy across the city, and on 13 September in a wide-ranging proclamation in support of their actions, Charles II instructed the Lord Mayor and City to:
cause an exact survey to be made and taken of the whole ruins occasioned by the late lamentable fire, to the end that it may appear to whom all of the houses and around did in truth belong, what term the several occupiers were possessed of, and what rents, and to whom, either corporations, companies, or single persons, the reversion and inheritance appertained: that so provision may be made, that though every man must not be suffered to erect what buildings and where he pleases, he shall not in any degree be debarred from receiving the reasonable benefit of what ought to accrue to him … we shall cause a plot or model to be made for the whole building through those ruined places: which being well examined by all those persons who have most concernment as well as experience, we make no question but all men will be pleased with it, and very willingly conform to those orders and rules which shall be agreed for the pursuing thereof.
The initial hope of the King and the City was to rebuild London on a grand scale as a completely new city, but they realised very quickly that speed was of the essence, and that the rebuilding programme must start as soon as possible (which meant in the spring of 1667, when the winter was over) or haphazard illegal construction would begin, and the homeless citizenry would become restless. It was with this in mind that the plans submitted while the ground was still hot were, though widely admired, rejected. First off the mark was Christopher Wren, who presented his idea for a new city to the King on 11 September; he was quickly followed by John Evelyn, who presented his own proposal to Charles two days later. These direct approaches to Charles upset Oldenburg, who felt that an opportunity to promote the Royal Society had been missed. Both Wren and Evelyn were Fellows, and if the plans had gone first to the Royal and then on to the King in the name of the Royal it would have benefited the Society. Hooke was more diplomatic. His plan, probably endorsed by Sir John Lawrence, was shown first to the City and then to the Royal, at a meeting held on 19 September. Only then was it presented to the King. Hooke’s proposal, we are told by Richard Waller, was for a rectangular layout of streets, a grid like the layout of many modern American cities, but the original plan has been lost. In any case, all these ideas (and a couple of others) came to naught. Because of the need for speed, it was decided to rebuild the city essentially along the old lines, literally building on the old foundations, but with some streets being widened and proper provision being made for facilities such as markets. The joint responsibility for getting this done was shared by the Privy Council (on behalf of the King) and the Court of Aldermen, representing the City. On 4 October 1666, a meeting of the Court considered a report from the Privy Council, and made the declaration that since:
for the better and more expedition of this work [the King] hath pleased to appoint Dr Wren Mr May and Mr Pratt to joyne with such Surveyors & Artificers as should be appointed by the City to take an Exact & speedy survey of all Streetes Lanes Aleys houses & places destroyed by the late dismall Fire That every particular Interest may be ascertained & provided for & the better Judgment made of the whole Affaire This Court doth therefore Order that Mr Hooke Reader of the Mathematicks in Gresham Collidge Mr Mills and Mr Edward Jermyn do joyne with the said Dr Wren Mr May & Mr Pratt in taking the said Surveigh …
There was clearly a delicate balancing act going on here. The three Royal appointees, known as ‘the King’s Commissioners’,fn6 had all been advising Charles, before the fire, on plans to repair the old St Paul’s Cathedral, which was now beyond repair and would have to be replaced by a new cathedral. The three City appointees, known as ‘the City Surveyors’,fn7 were chosen to match the number of King’s Commissioners, and perhaps with an eye on matching them intellectually, or academically, as well. Peter Mills was an obvious appointment; he was already the City Surveyor, and one of the people who had drawn up a plan for the rebuilding. Edward Jermyn (or Jerman) turned down the appointment (probably because he had a busy and lucrative private architectural practice);